GCC Version 6 doesn't build a working HotSpot without two flags: -fno-delete-null-pointer-checks -fno-lifetime-dse
These are because HotSpot uses undefined behaviour in some places. "-fno-delete-null-pointer-checks" is needed because HotSpot dereferences null pointers in soe places. "-fno-lifetime-dse" refers to the practice of initializing objects before the start of a constructor, which is explicitly forbidden by Standard C++, but is used by HotSpot. GCC 6 is quite new, so we have a little time before the various users of OpenJDK start to hit these problems, but I'd like to help get some build fixes in as soon as we can. Also, it's not just about JDK9: 8u fails to build too. Thanks, Andrew.
